+def get_format_from_string(txt):
+ """
+ Returns the SourceFormat class that corresponds to the specified .changes
+ Format value. If the string does not match any class, UnknownFormatError
+ is raised.
+ """
+
+ for format in srcformats:
+ if format.re_format.match(txt):
+ return format
+
+ raise UnknownFormatError, "Unknown format %r" % txt
+